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Questions and Answers
What is the shape of the pelvic inlet/brim?
What is the shape of the pelvic inlet/brim?
What is the anterior-posterior diameter measurement of the obstetrical conjugate?
What is the anterior-posterior diameter measurement of the obstetrical conjugate?
What angle does the pelvic outlet slope at to the horizontal?
What angle does the pelvic outlet slope at to the horizontal?
Which muscle plays a key role in supporting the pelvic floor during childbirth?
Which muscle plays a key role in supporting the pelvic floor during childbirth?
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What serves as a landmark for assessing pelvic excavation during labor?
What serves as a landmark for assessing pelvic excavation during labor?
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Which structure provides support and stability to the perineal body?
Which structure provides support and stability to the perineal body?
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Which pelvic measurements are critical in determining whether the foetal head will engage with the pelvic brim?
Which pelvic measurements are critical in determining whether the foetal head will engage with the pelvic brim?
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What is the role of the axis of the pelvic canal during labor?
What is the role of the axis of the pelvic canal during labor?
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What is the anterior-posterior diameter measurement of the pelvic outlet?
What is the anterior-posterior diameter measurement of the pelvic outlet?
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Which muscle forms part of the pelvic floor and is shaped like a hammock?
Which muscle forms part of the pelvic floor and is shaped like a hammock?
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What is the shape of the pelvic outlet?
What is the shape of the pelvic outlet?
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The right sacro-cotyloid diameter measures how much?
The right sacro-cotyloid diameter measures how much?
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Which measurement is not part of the pelvic cavity boundaries?
Which measurement is not part of the pelvic cavity boundaries?
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What is the transverse diameter measurement between the ischial tuberosities in the pelvic outlet?
What is the transverse diameter measurement between the ischial tuberosities in the pelvic outlet?
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What is the length of the posterior wall of the pelvic cavity?
What is the length of the posterior wall of the pelvic cavity?
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Which structure is essential for providing strong support for the pelvic contents?
Which structure is essential for providing strong support for the pelvic contents?
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Which bone forms the upper part of the greater sciatic notch?
Which bone forms the upper part of the greater sciatic notch?
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What structure is characterized as the lateral bony prominence below the acetabulum?
What structure is characterized as the lateral bony prominence below the acetabulum?
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Which part of the innominate bone fuses with the pubis at the ilio-pectineal eminence?
Which part of the innominate bone fuses with the pubis at the ilio-pectineal eminence?
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What does the inferior ramus of the pubis form when it joins with the ischium?
What does the inferior ramus of the pubis form when it joins with the ischium?
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What is the function of the sacral hiatus?
What is the function of the sacral hiatus?
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Which structure is primarily responsible for separating the greater and lesser sciatic notches?
Which structure is primarily responsible for separating the greater and lesser sciatic notches?
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Which aspect of the ilium is concave and smooth, forming the iliac fossa?
Which aspect of the ilium is concave and smooth, forming the iliac fossa?
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Which pairs of foramina are formed from the fused intervertebral notches for the passage of sacral nerves?
Which pairs of foramina are formed from the fused intervertebral notches for the passage of sacral nerves?
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Study Notes
Pelvic Anatomy
- The pelvis is comprised of 3 bones: ilium, ischium, and pubis.
- The pelvis provides a protective framework for pelvic organs and supports the trunk.
- The pelvis is a bony canal for the passage of the foetus.
- The pelvis is divided into three sections: pelvic inlet/brim, pelvic cavity, and pelvic outlet.
Pelvic Inlet/Brim
- The pelvic inlet is the top opening of the pelvis.
- It is shaped like a circle or oval and has a circumference of approximately 40cm.
- The boundaries of the pelvic inlet are the sacral promontory, sacral alae, sacro-iliac joint, ilio-pectineal line, ilio-pectineal eminence, superior ramus of pubis, and symphysis pubis.
- The obstetrical conjugate is a key measurement of the pelvic inlet, measuring 11cm.
Pelvic Cavity
- The pelvic cavity extends from the brim to the outlet and is shaped like a circle.
- It is comprised of four walls: posterior, anterior, and two lateral.
- The anterior wall is 4cm long and comprises the pubis.
- The posterior wall is 12cm long and comprises the sacrum.
Pelvic Outlet
- The pelvic outlet is the bottom opening of the pelvis.
- It is diamond-shaped and is comprised of the tip of the coccyx, sacro-tuberous ligament, ischial tuberosity, pubic arch, and lower border of the symphysis pubis.
- The size of the pelvic outlet varies depending on the movement of the coccyx.
- The transverse diameter is approximately 11cm, but tissue can reduce it by at least 1.2cm.
Pelvic Floor Muscles
- The pelvic floor is made up of muscles and fascia.
- It is shaped like a hammock.
- It provides strong support for the pelvic organs.
Planes and Measurements of a Gynaecoid Pelvis
- The pelvic planes are imaginary flat surfaces that pass across the pelvic canal at different levels.
- The pelvic inclination is the angle at which the pelvis slopes relative to the horizontal.
- The plane of the pelvic outlet is at a lesser angle than the plane of the pelvic inlet, causing the foetus to turn as it descends through the pelvis.
- The axis of the pelvic canal is an imaginary line drawn at right angles through the centre of each plane.
- Traction applied with forceps or vacuum must follow the axis of the pelvic canal.
Pelvic Measurements
-
Pelvic Inlet:
- Anatomical/True Conjugate: 12cm
- Obstetrical Conjugate: 11cm
- Oblique Diameter: 12cm
- Transverse Diameter: 13cm
-
Pelvic Cavity:
- Anterior Posterior Diameter: 12cm
- Oblique Diameter: 12cm
- Transverse Diameter: 12cm
- Between the ischial spines: 10cm
-
Pelvic Outlet:
- Anterior-Posterior Diameter: 13cm
- Oblique Diameter: 12cm
- Transverse Diameter: 11cm
Bones of the Pelvis
-
Innominate Bone:
- Consists of three bones that fuse together during adulthood
- Ilium: Forms the upper part of the acetabulum and the greater sciatic notch.
- Ischium: Forms the lower portion of the acetabulum, the side wall of the true pelvis, and the lower boundary of the obturator foramen.
- Pubis: Forms the anterior portion of the pelvis and the upper boundary of the obturator foramen.
- Consists of three bones that fuse together during adulthood
-
Sacrum: Five fused vertebrae that form the posterior wall of the pelvis. Key structures include:
- Sacral promontory
- Sacral alae
- Sacral hiatus
- Sacral cornua
- Foramina
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Description
Test your knowledge of pelvic anatomy, including the structure and function of the pelvis, its sections, and key measurements. This quiz will cover important concepts related to the pelvic inlet, cavity, and outlet.
